Light-developable silver halide emulsions



United States Patent 3,287,137 LIGHT-DEVELOPABLE SILVER HALIDE EMULSIONSClarence E. McBride, Rochester, N.Y., assignor to Eastman Kodak Company,Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 23,1964, Ser. No. 406,165 19 Claims. (31. 96--107) This application is acontinuation-in-part of my copending application, U.S. Serial No.222,964, filed September 11, 1962, now abandoned and my copendingapplication, U.S. Serial No. 394,062, filed September 2, 1964.

The present invention relates to photography, and more particularly tolight-developable, direct-print photographic silver halide emulsions.

Radiation-sensitive papers adapted for light recording, e.g.,oscillographic recording, are known. Typical of such papers are thedeveloping-out and print-out type. The developing-out type, as the nameimplies, requires that the exposed material be chemically developed,fixed and washed in order to provide a stable visible image on saidmaterial. The print-out type of material develops on exposure andrequires no development step. The printout type is generally much slowerthan the developingout type and the images are unstable and have a shortlife.

A third type of radiation-sensitive material especially suitablerforlight-writing and oscillographic recording comprises a hydrophiliccolloid-silver halide emulsion layer which, when exposed to a highintensity source of electromagnetic radiation, forms a latent imagewhich can then be developed by subsequent general exposure to a secondsource of radiation of lower intensity. Such direct-writing ordirect-print emulsions are faster than print-out emulsions and requireno chemical development. However, many of the recording papers of thisthird type have a slow rate of photodevelopment and the background areastend to build up to obscure the image on subsequent exposure to light.

It is an object of this invention to provide a new class oflight-developable, direct-print, radiation-sensitive silver halideemulsions.

It is another object of this invention to provide novel photographicsilver halide emulsions suitable for preparing direct-print recordingphotographic elements that can be exposed to a high intensity trace andthereafter photodeveloped to produce images particularly characterizedas having low D or background density.

It is still another object of this invention to provide newphotodevelopable photographic silver halide emulsions that arecharacterized as having high density differential between theinitially-exposed and unexposed areas upon photodevelopment.

It is also an object of this invention to provide new photodevelopablephotographic silver halide emulsions containing novel cooperating orsynergistic addenda for such emulsions.

These and other objects of the invention are accomplished with alight-developable, direct-print silver halide emulsion containing anitrogen-containing halogen acceptor and wherein the silver halidegrains of the emulsion are formed in the presence of lead ions.

The nitrogen-containing halogen acceptors used in the emulsions of theinvention can be represented by the formulas,

wherein: R, R and R can each be hydrogen atoms, alkyl Ice radicals, arylradicals, including substituted alkyl and aryl radicals, or acylradicals (e.g.,

wherein R is a hydrogen atom, an alkyl radical or an aryl radical); Rcan be a nitrogen-containing radical such as an amino radical or athiocarbamyl radical, including substituted amino and thiocarbamylradicals; and D represents the necessary atoms to complete aheterocyclic nucleus generally having 5 or 6 atoms including at leasttwo nitrogen atoms and at least one divalent radical having the formula,

wherein X can be a sulfur atom, an oxygen atom, a selenium atom or animino radical (=NH). When a nitrogen atom comprising D or R is attacheddirectly to the nitrogen atoms of the above formulas, at least onehydrogen atom is attached to at least one of such nitrogen atoms of thehalogen acceptor. The amino radical for substituent R can be representedby the formula,

wherein R and R can be the same snbstituents as R and R or aminoradicals.

Particularly useful nitrogen-containing halogen acceptors used in theemulsions of the invention can be further repr sented by the followingsubgeneric formulas:

wherein: R R R R R R R R R" and R can each be hydrogen atoms, alkylradicals, aryl radicals or acyl radicals as described above for R and Rcan be a sulfur atom, an oxygen atom, a selenium atom or an iminoradical; and Q and Z can be the necessary atoms to complete aheterocyclic nucleus generally having 5 or 6 members. Q and Z typicallyare the necessary atoms to complete such moieties as a triazole-thiol, amercaptoimidazole, an imidazolidine-thione, a triazine-thiol, athiobarbituric acid, a thiouracil, a urazole including a thiourazole andthe like heterocyclic moieties.

With respect to the above formulas of nitrogen-containing halogenacceptors: the aryl radical substituents are those of the naphthyl andphenyl' series, and include such common substituents as alkyl groups,halogen atoms, acyl radicals and the like; the alkyl radicalsubstituents typically can contain 1 to 20 carbon atoms and moregenerally 1w 8 carbon atoms, and can be substituted with such radicalsas aryl radicals, halogen atoms, acyl radicals and the like.

Typical halogen acceptors of the thiourea type represented by Formula Aand Formula B are disclosed in copending Kitze application, U.S. SerialNo. 303,146 filed August 19, 1963, now US. Patent No. 3,241,971;

and in copending Fix application, U.S. Serial No. 338,605,

filed January 20, 1964. Typical halogen acceptors of the hydrazine typerepresented by Formula C are disclosed in Ives, US. Patent 2,588,982,issued March 11, 1952. Typical halogen acceptors of the type representedby Formula D are the urazole and thiourazole halogen acceptors disclosedin Bacon and Illingsworth application, titled Light-DevelopableDirect-Print Silver Halide Emulsions, which was filed concurrentlyherewith.

Examples of specific nitrogen-containing halogen acceptors are set outbelow.

1,3-dimethyl-2-imidazolidinethione 2-imidazolindinethione1-phenyl-5-mercaptotetrazole Thiosemicarbazide Tetramethylthioureap-Dimet-hylaminobenzaldehyde-thiosemicarbazone l-isopentyl-Z-thiourea1-(2-diethylarninoethyl)-1,2,'5,6-tetrahydro-1,3,5-triazine- 4-thio11,2bis( 1,2,5 ,G-tetrahydro-1,3,5-triazine-4-thiol)ethanel-phenyl-Z-thiourea 1,3-diphenyl-2-thiourea 4-thiobarbi-turic acidZ-thiouracil l-acetyl-Z-thiourea 1 ,3-dibenzyl-2-thiourea1,1-diphenyl-2-thiourea 1-ethy1-1-( a-napthyl)-2-thioureaZ-mercaptoimidazole 1-phenyl-2-imidazolindinethione4,5-diphenyl-4-imidazolidine-Z-thione l-methyl-2-mercaptoimidazole1-n-butyl-1,2,5,6-tetrahydro- 1,3,5-triazine-4-thiol Thiourea1-rnethyl-2-imidazolindinethione D-mannose thiosemicarbazoneMorpholino2-propane thiosemicarbazone D-galactose thiosemicarbazoneUrazole 3-thiourazole 3,5 -dithourazole 3,5 -dithiourazole hydrazinesalt 4-aminourazole hydrazine salt 3,5-dithiourlazole hydrazine saltUrazole sodium salt 4-( 1-napthyl)urazole 4-ethylurazole l-phenylurazole4-phenylu-razole l-butylurazole l-octylurazole 4-b utyl-3 ,5-dithiourazole 1,4-diphenylurazole 4 1,4-dibutylurazole1,4-dibutyl-3,S-dithiourazole 1,4-diphenyl-3,S-dithiourazole1-ethyl-4-phenylurazole 1-ethyl-4-pl1enyl-3,S-dithiourazole3-thio-5-iminourazole 5-selenourazole Hydrazine Phenylhydrazinehydrochloride 2,5 -dichlorophenyl hydrazine p-Tolylhydrazinehydrochloride a-Naphthylhydrazine a-Benzyl-a-phenylhydrazine p-Toluenesulfonyl hydrazine Hexylhydrazine bromide, silver bromoiodide, .silverchloroiodide, and, The preferred emulsions are,

silver chlorobromoiodide. those wherein the halide of the silver halideis predominantly bromide. For a description of suitable emulsions,

reference is made to Davey et :al., US. Patent 2,592,250,

issued April 8, 1952; Glafkides, Photographic Chemistry, vol. 1, pp.31-2, Fountain Press, London; and my copending application, Serial No.222,964, filed September 1-1, 1962, wherein is disclosed the preparationof silver halide emulsions with organic thioether silver halide solventspresent during the grain growth of the silver halide. In myabove-mentioned copending application is taught the addition of thethioether silver halide solvent to the colloidal material in which thesilver halide is precipitated, during the precipitation of the silverhalide or to the silver halide prior to or during the ripening of thesilver halide. Typical of such thioethers are 3,6-dithia-1,8-octanediol,1,10 dithia 4,7,13,16-tetraoxacyclooctadecane, 7,10-diaza 1,16dicarboxamido-S;l4-dithia1hexadecane-6,1l-dione, and1,17-di-(N-ethylcarbamyl)-6,l2-dithia-9-oxahep tadecane. The amount ofthioether utilized to prepare the silver halide emulsions described inmy copending application can be widely varied although about .1 to 25 g.of thioether per mole of silver halide is generally utilized. Thepresent silver halide emulsions generally have an average grain size ofabout .1 to 10 microns, and more generally about .5 to l micron.

The so-called internal image emulsions can be used in the invention,such having silver halide grains wherein a predominant amount of thesensitivity is internal to the grains. Such internal image emulsions arethose which, when measured according to normal photographic techniquesby coating a test portion of the emulsion on a greater than thesensitivity of an identical test portion which has been exposed in thesame way and developed for 6 minutes at 68 F. in Developer A below (asurface. type developer).

DEVELOPER A G. N-methyl-p-aminophenol sulfate 0.31 Sodium sulfite,desiccated 39.6 Hydroquinone 6.0'

DEVELOPER AContinued Water to make 1 liter A wide variety ofhydrophilic', water-permeable organic colloids can be suitably utilizedin preparing the silver halide emulsions or dispersions of theinvention. Gelatin is preferably utilized although other colloidalmaterial such as colloidal albumin, cellulose derivatives, syntheticresins or the like can be utilized. Suitable colloids that can be usedare polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described inLowe, US. Patent 2,286,- 215, issued June 16, 1942; a far hydrolyzedcellulose ester such as cellulose acetate hydrolyzed to an acetylcontent of 19 to 26% as described in US. Patent 2,327,- 808 of Lowe andClark, issued August 24, 1943; a watersoluble ethanolamine celluloseacetate as described in Yutzy, US. Patent 2,322,085, issued June 15,1943; a polyacrylamide having a combined acrylamide content of 30 to 60%and a specific viscosity of 0.25 to 1.5 on an imidized polyacrlyamide oflike aorylamide content and viscosity as described in Lowe, Minsk andKenyon, US. Patent 2,541,474, issued February 13, 1951; zein asdescribed in Lowe, US. Patent 2,563,791, issued August 7, 1951; a vinylalcohol polymer containing urethane carboxylic acid groups of the typedescribed in Unruh and Smith, US. Patent 2,768,154, issued October 23,1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinylcyanoacetate copolymer as described in Unruh, Smith and Priest, US.Patent 2,808,331, issued October 1, 1957; or a polymeric material whichresults from polymerizing a protein or a saturated acylated protein witha monomer having a vinyl group as described in Illingsworth, Dann andGates US. Patent 2,852,382, issued September 19, 1958. Mixtures of suchorganic colloids can also be used.

Although silver halide emulsions are generally made with an equivalentor slight excess of halide ion present, I have found it desirable to addadditional water-soluble iodide t the silver halide emulsion after itsprecipitation but before it is coated. More generally, about .1 to 50mole percent, and preferably about 1 to 10 mole percent of water-solubleiodide based on the silver halide in the emulsion is used. Illustrativewater-soluble iodides include ammonium, calcium, lithium, magnesium,potassium, or sodium iodide.

Lead ions are used in the precipitation or formation of the silverhalide of the emulsions of the invention. Watersoluble lead salts aresuitably added with the water-soluble silver salt to an appropriateWater-soluble halide to precipitate the lead-silver halide of thepresent emulsions. Typical suitable water-soluble lead or plumbous saltsinclude lead acetate, lead nitrate, lead cyanide, and the like. Theamount of lead utilized in the silver halide of the emulsions of theinvention suitably ranges from about .01 to 5 mole percent based on thesilver halide. The presence of a water-soluble lead salt during thesilver halide formation or grain growth when preparing thelight-developable, direct-print emulsions of the invention is to bedistinguished from the addition of a Water-soluble lead salt shortlyprior to coating and after the silver halide grains have been formed.

The subject photodevelopable photographic silver halide emulsions of theinvention can contain the addenda generally utilized in such productsincluding gelatin hardeners, gelatin plasticizers, coating aids and thelike, as well as spectral senstitizing dyes of the type described incopending Jones application, U.S. Serial No. 380,044, filed July 2,1964.

The above-described emulsions of the invention can be coated on a widevariety of supports in accordance with usual practice. Typical supportsfor photographic elements of the invention include paper, glass,cellulose nitrate film, cellulose acetate film, polyvinyl acetal film,polystyrene-film, polyethyleneterephthalate film and related films ofresinous materials and others.

In forming a photodeveloped image with a typical photographic elementcontaining an emulsion of the invention, the photographic element isinitially exposed to a relatively short duration and high intensitysource of electromagnetic radiation (e.g., at least about .1 footcandlesecond at an intensity of more than about 100 foot-candles) such as ahigh intensity light source rich in blue and ultraviolet light such asare used in oscillographs described in Heiland, US. Patent 2,580,427,issued January 1, 1952, high intensity visible light, X-radiation andthe like, to form a latent image in the emulsion of the photographicelement, and thereafter the resulting latent image is photodeveloped byoverall exposure of the emulsion to a radiation source of lowerintensity than the original exposure, such as to a conventionalfluorescent light, light from incandescent lamps commonly used forgeneral illumination, or even ordinary daylight. Generally, the latentimage formed in the emulsion in the first instance is not visible anddoes not become visible until photodevelopment. Heat is desirablyutilized during the photodevelopment step. Typically the subjectemulsions are heated to a temperature of about C. to 200 C. for about 1to 30 seconds and photodeveloped after the initial high intensityexposure.

The invention is further illustrated by the following examples ofpreferred embodiments thereof.

Example 1 A light-developable, direct-print, large-grain gelatin-silverchlorobromide emulsion mole percent bromide, 5 mole percent chloride)having silver halide grains of high internal sensitivity was prepared byslowly adding 21 aqueous solution of silver nitrate containing .85 g. oflead nitrate per mole of silver to an agitated gelatin solutioncontaining a stoichiometric excess of potassium chloride and potassiumbromide, .5 g. of a thioether silver halide solvent of the typedescribed in my said application Serial No. 222,964 per mole of silverhalide also being added during the silver halide precipitation. Theemulsion was washed with water to remove Water-soluble salts. Theprepared emulsion was divided up into several portions and to each ofsuch portions of emulsion was added a nitrogen-containing halogenacceptor as indicated in Table I below. The resulting emulsions werecoated on paper supports at a silver coverage of 258 mg. per square footand at a gelatin coverage of 565 mg. per square foot. Strips of eachcoating containing various halogen acceptors, as well as a correspondingstrip containing no halogen acceptor, were image-exposed, wherein theimage constituted opaque bars with a high intensity xenon lamp (HeilandStrobonar watt-second xenon lamp for about .002 second at a distance ofabout 8 feet) and photodeveloped for 5 minutes with a 60 footcandle coolwhite fluorescent light. Table I below summarizes the densities of theimage or exposure areas (D the densities of the background or unexposedareas (D and the density differences between such areas (AD) for each ofthe coatings, The concentration of halogen acceptor indicated in Table Iis in mole percent based on the silver halide in the emulsion.

TABLE I Nitrogen-Containing Halogen Acceptor Dmn! Dmin D None 21 13 08Urazole, 16% mole percent 56 18 38 3 thiourazole, 5 mole percent..- 5818 40 3,5-dithiourazole, 5 mole percent 61 18 43 3,5-dithiourazolehydrazine salt, 4 mole percent 70 21 49 -ethylurazole, 15 mole percent43 14 29 l-phenylurazole, 15 mole percent 36 13 23 4-phenylurazole, 15mole percent 38 13 25 4-aminourazole hydrazine salt, 5 mole percent. 6117 44 3-thio-5-iminourazole, 4.7 mole percent 57 l7 40 Hydrazinehydrochloride, 5 mole percent 51 16 35 Hydrazine hydrochloride, 12 molepercent 60 l8 42 Carbohydrazide, 10 mole percent 61 18 43 Dithiobiurea,1 mole percent 61 17 44 As can be observed from the data set out in thetable above, light-developable, direct-print silver halide emulsionscontaining a wide variety of halogen acceptors can be utilized toimprove the utility of silver halide emulsions wherein lead ions arepresent during the formation of the silver halide grains. ings can bechemically developed and fixed to form archival quality images, a 1minute development and a 1.5 minute fix at 72 F. in the following bathsbeing suitable:

DEVELOPING COMPOSITION Water to make one liter.

Example 2 A sample of the light-developable, direct-print silver halideemulsion containing 4.7 mole percent of 3-iminothiouradole and coated ona paper support as described in Example 1 was incubated at 120 F. and35% relative humidity for 7 days prior to being exposed andphotodeveloped as described in Example 1. The density of the resulting Dor image area was .53 and the density of the D or background area Was.15 and AD or D D was .38.

Example 3 A light-developable, direct-print silver halide emulsion asdescribed in Example 1 was prepared and coatings were preparedcontaining 5, l and 40 mole percent of urazole based on the silverhalide. The coatings contained silver at a coverage of 258 mg. persquare foot and gelatin at a coverage of 565 mg. per square foot. Eachof the coattings were exposed on an Edgerton, Germeshausen and GrierMark VII sensitometer containing a xenon flash lamp for 10 microsecondsthrough a 0.15 log E density, increment neutral density step tabletfollowed by a photodevelopment of minutes with a 60 foot-candle coolwhite fluorescent light. Good image discrimination of the magnitudeillustrated by the data set out in the table above was obtained for eachof the coatings after the exposure and photodevelopment.

Example 4 A light-developable, direct-print silver halide emulsion asdescribed in Example 1 was prepared and coatings were prepared both withand without 5 mole percent of the If desired, the exposedcoatnitrogen-containing halogen acceptor, 3,5-dithiourazole hydrazinesalt, as well as with a silver halide emulsion in which the silverhalide was precipitated in the absence of lead nitrate. The variouscoatings were then exposed and photodeveloped as described in Example 1.The D and D values were then determined for the respective coatings, andwhich values are summarized in Table II below.

TABLE II Feature Addenda Din-x Dmln AD (8-) N (b) Lead nitrate, .85gJmole silver halide... 21 13 08 (c) 3,5-Dithiourazole hydrazine salt, 5mole .57 .39 .18

percent. (d) (b)+(c) .59 17 .42

1 No image.

As can be observed from the data summarized in Table II,nitrogen-containing halogen acceptors cooperate synergistically with thefeature of forming the silver halide in the presence of lead ions inlight-developable, directprint silver halide emulsions. tion exhibited adesirably low background density (Di and a high degree of imagediscrimination (AD).

Example 5 A light-developable, direct-print, light-sensitive large-'grain gelatin-silver chlorobromoiodide emulsion (95.21 mole percentbromide, 4.5 mole percent chloride, 0.34 mole percent iodide) havingsilver halide grains of high internal sensitivity was prepared by slowlyadding an lead nitrate per mole of silver halide added to the coatingmelt just prior to coating. Emulsion B was coated without any additionallead nitrate added. Also, coatings, of Emulsions A and B contained thenitrogen-containing halogen acceptor, imidazolidine-Z-thione, atconcentrations of .236 g. per mole of silver halide in the emulsions.The coatings also each contained 1.65 g. of potassium iodide per mole ofsilver halide in the emulsions. All of the coatings were made onphotographic paper supports at coverages of 256 mg. of silver per squarefoot and 558 mg. of gelatin per square foot. The coatings were exposedto a xenon flash lamp and photodeveloped' as described in Example 3. Theresults are summarized by the data set out in Table III below.

1 Lead nitrate added during precipitation of the silver halide. 1Imrdazolidine-Z-thione (ethylenethiourea).

As can be observed from the data set out in Table III,

emulsions with silver halide grains formed in the presence of awater-soluble lead salt, as was the case with Emulsion B, cooperate withthe nitrogen-containing halogen acceptor to result in direct-printimages having lower D or density in background areas and better imagediscrimination(D -D or AD) than result with comparable emulsions whereinthe water-soluble lead salt is added to the emulsion just prior tocoating. Similar Coating (d) of the inven- 9 results are obtained if .45g. of dithiobiurea per mole of silver halide in the emulsion weresubstituted for the imidazolidine-Z-thione.

Example 6 A large-grain gelatin-silver chlorobromide light-developabledirect-print emulsion (95% bromide, chloride) having high internalsensitivity and low surface sensitivity was prepared by slowly adding anaqueous solution of silver nitrate containing .85 g. of lead nitrate permole of silver to an aqueous gelatin solution containing astoichiometric excess of potassium chloride and potassium bromide, .5 g.of a thioether silver halide solvent of the type described in my saidapplication Serial No. 222,964, per mole of silver halide being addedduring the resulting precipitation. The emulsion was washed with waterto remove water-soluble salts. To separate portions of this emulsionwere added typical feature nitrogen-containing halogen acceptors asdescribed in Table IV below and coated on paper supports at coverages of258 mg. of silver per square foot and 560 mg. of gelatin per squarefoot. The coatingswere exposed to a IOU-microsecond flash on anEdgerton, Germeshausen and Grier Mark VI sensitometer containing a xenonlight source through a 0.15 log E neutral density step tablet andthereafter photodeveloped for 5 minutes with a 60 footcandle, cool-whitefluorescent light source. The number of visible 0.15 log E stepsobtained for the various coatings is summarized in Table IV. Also, thedensity difierence between image and background after the 5 minutephotodevelopment was observed for the various coatings, and whichdensity differences are recorded in Table IV as AD. In the variouscoatings the potassium iodide (K1) was used at concentrations of 2.1mole percent based on the silver halide and the nitrogen-containinghalogen acceptors were used at concentrations of 3.7 mole percent basedon the silver halide unless otherwise indicated.

TABLE IV Visible 0.15 log Emulsion Addenda E Steps on AD Exposure andPhotodevelopment;

(1) K 15 37 (2) 1-n-butyl-1,2,5,6-tetrahydro-l,3,5-triazine- 4-thiol 1628 (3) l-n-butyl-l,2,5,6-tetrahydro-1,3,5-triaziue- 4-thi0l KI 17 48 (4)1-n-butyl-1,2,5,6-tetrahydro-1,3 fi-trlazine- 4-thiol (5.8 mole percent)16 28 (5) Tetramethylthiourea+KI 16+ 36 (6)1,3-dimethyl-2-imidazolinethione-l-KI 17 45 (7)3,4dipl1enyl-5-mercapto-1,2,4-triazole+KI 15 41 (8)4-pl1euyl-3-mercapto-1,2,4-triazole+Kl 16+ 39 (9) 2-mercaptoimidazole+KI16+ 41 (10) 1-methyl-2-mercaptoi.midzole+KI 16+ .40 (11)2-mercaptoimidazoline+KI 17 42 (12) 1-phenyl-2-mercaptoimidazoline+KI16+ 42 (13) l,3-dimethyl-2-merepatoimidazoline+KI 16+ .39 (14)5,5-dimethy1-Lmercaptohydautoin+KI 15 39 (15)4,5-diphenyl-Z-mercaptoimjdazoline+KI. 16+ 4O (16)1,1-diphenyl-2-thiourea+KI 15+ 43 (17)1,3-di-m-methoxyphenyl)-2-thiourea 16 41 (18)l-(o-methoxyphenyl)-2-thiourea+KI- 15+ 45 9)1-(p-methoxyphenyl)-2-thiourea+KI 16+ .45 (20)1-methyl-1,2,5,fi-tetrahydrot-mercapto-l,

3,5-triazine+KI 16+ 38 (21) 4-thiobarbituric acid+K 15 .44 (22)1-al1y1-2-thiourea+KI 17 .44 (23) 2-thi0uraeil+KI 16 38 (24)1-acetyl-2thiourea+KI 16+ 45 (25) l-ethyl-l-(a-naphthyl)-2'thiourea+KI16 40 (26) 2-imidazolidinethione+KI 17 47 (27)l-isopentyl-Z-thiourea-l-KI 17 45 (28)l-(2-diethylaminoethyl)-1,2,5,6-tetrahydroA-mercapto-l,3,5-triazine+KIl7 41 (29) 1,2-bis(1,2,5,fi tetrahydroi mercaptotriazine)-ethane+KI 1742 (30) +ethy1carboxymethyl-1,2,5,6-tetrahydro-4-mercapto-1,3,5-triazine+KI 17 45 (31) 1-phenyl-2-thi0urea+KI 17 42(32) Thiourea+KI 17 44 As can be observed from the data set out in TableIV, a wide variety of nitrogen-containing halogen acceptors can 10 beutilized in the light-developable, direct-print leadsilver halideemulsions of the invention.

The silver halide of the emulsions of the invention described in theexamples above were all formed or precipitated in the presence of leadions in acidic media (about pH 2, sulfuric or nitric acid beingutilized). The emulsions of the invention also all containednitrogen-containing halogen acceptors. Such emulsions were demonstratedto be useful light-developable, direct-print emul- The invention hasbeen described in considerable detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

I claim:

1. A light-developable, direct-print silver halide emulsion containing anitrogen-containing halogen acceptor wherein the substituents:

(A) R, R and R are each selected from the group consisting of a hydrogenatom, an alkyl radical, an aryl radical and an acyl radical;

(B) R is a nitrogen-containing radical selected from the groupconsisting of a thiocarbamyl radical and an amino radical; and

(C) D represents the atoms necessary to complete a heterocyclic nucleushaving 5 to 6 atoms including at least two nitrogen atoms and at leastone divalent radical having the formula X [I C wherein X is selectedfrom the group consisting of and oxygen atom, a sulfur atom, a seleniumatom and an imino radical;

except that when a nitrogen atom comprising one of said substituents isattached directly to a nitrogen atom of one of said formulas, thehalogen acceptor contains at least one hydrogen atom attached to atleast one of said nitrogen atoms.

2. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent of lead ions based on the silver halide, and said silverhalide emulsion contains a nitrogen-containing halogen acceptor havingthe formula wherein D represents the atoms necessary to complete aheterocyclic nucleus having 5 to 6 atoms including at least one divalentradical having the formula s H .C

and at least two nitrogen atoms.

3. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent of lead ions based on the silver halide, and said silverhalide emulsion contains a nitrogen-containing halogen acceptor havingthe formula wherein R is an amino radical.

5. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 tomole percent of lead ions based on the silver halide, and said silverhalide emulsion contains a nitrogen-containing halogen acceptor havingthe formula wherein R is a thiocarbamyl radical.

6. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent of lead ions based on the silver halide, and said silverhalide emulsion contains a nitrogen-containing halogen acceptor havingthe formula wherein R and R are each amino radicals.

, 7. A light-developable, direct-print silver halide emulsion whereinthe silver halide grains have been formed in the presence of about .01to 5 mole percent of lead ions based on the silver halide, and saidsilver halide emulsion contains a nitrogen-containing halogen acceptorhaving the formula HN-i'i-NE wherein Q represents the atoms necessary tocomplete a heterocyclic nucleus having 5 to 6 atoms.

8. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent of lead ions based on the silver halide, and said silverhalide emulsion contains a nitrogen-containing halogen acceptor havingthe formula R-N--C-N-R wherein Q represents the atoms necessary tocomplete a heterocyclic nucleus having 5 to 6 atoms and R is an alkylradical.

9. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about..01 to 5mole percent of lead ions based on the silver halide, and said silverhalide emulsion contains a nitrogen-containing halogen acceptor havingthe formula I HD T( iI IR wherein Q represents the atoms necessary tocomplete a heterocyclic nucleus having 5 to 6 atoms and R is a phenylradical.

10. A light-developable, direct-print silver halide ecmulsion whereinthe silver halide grains have been formed 12. in the presence of about.01 to 5 mole percent of lead ions based on the silver halide, and saidsilver halide emulsion contains a nitrogen-containing halogen acceptorhaving the formula wherein Q represents the atoms necessary to completea heterocyclic nucleus having 5 to 6 atoms and Ris an alkyl radical.

11. A light-developable', direct-print silver halide emulsion whereinthe silver halide grains have been formed in the presence of about .01to 5 mole percent of lead ions based on the silver halide, and saidsilver halide emulsion contains a nitrogen-containing halogen acceptorhaving the formula wherein R is an amino radical.

12. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent of lead ions based on the silver halide, and said silverhalide emulsion contains a nitrogen-containing halogen acceptor havingthe formula wherein R R R and R are each alkyl radicals.

13. A light-developable, direct-print silver halide emul-. sion whereinthe silver halide grains have been formed in the presence of about .01to 5 mole percent of lead ions based on the silver halide, and saidsilver halide emulsion contains a nitrogen-containing halogen acceptorhaving the formula wherein Z represents the atoms necessary to completea thiourazole nucleus.

14. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent of lead ions based on the silver, halide, and said silverhalide emulsion contains a nitrogen-containing halogen acceptor havingthe formula wherein Z represents the atoms necessary to complete aurazole nucleus.

15. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent based on the silver halide of lead ions, said halide ofsaid silver halide being predominantly bromide, and saidsilver halideemulsion contains about .1 to mole percent based on said silver halideof 3,5-dithiourazole.

16. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent based on the silver halide of lead ions, said halide ofsaid silver halide being predominantly bromide, and said silver halide.emulsion contains about .1 to 100 mole percent based on said silverhalide of thionrea.

17. A light-developable, directaprint silver halide emulsion wherein thesilver halide grains have been formed 13 in the presence of about .01 to5 mole percent based on the silver halide of lead ions, said halide ofsaid silver halide being predominantly bromide, and said silver halideemulsion contains about .1 to 100 mole percent based on said silverhalide of urazole.

18. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent based on the silver halide of lead ions, said halide ofsaid silver halide being predominantly bromide, and said silver halideemulsion contains about .1 to 100 mole percent based on said silverhalide of imidazolidine-Z-thione.

19. A light-developable, direct-print silver halide emulsion wherein thesilver halide grains have been formed in the presence of about .01 to 5mole percent based on the silver halide of lead ions, said halide ofsaid silver halide being predominantly bromide, and said silver halideemulsion contains about .1 to 100 mole percent based on said silverhalide of dithiobiurea.

References Cited by the Examiner UNITED STATES PATENTS 5 NORMAN G.TORCHIN, Primary Examiner.

J. RAUBITSCHEK, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,287,137 November 22, 1966 Clarence E. McBride It is herebycertifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

R R Column 1, line 69, for read column 7, line N N 47, for "thiouradole"read thiourazole Signed and sealed this 5th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Commissioner of Patents AttestingOfficer

1. A LIGHT-DEVELOPABLE, DIRECT-PRINT SILVER HALIDE EMULSION CONTAINING ANITROGEN-CONTAINING HALOGEN ACCEPTOR AND WHEREIN THE SILVER HALIDEGRAINS OF SAID EMULSION HAVE BEEN FORMED IN THE PRESENCE OF LEAD IONS,SAID HALOGEN ACCEPTOR HAVING A FORMULA SELECTED FROM THE GROUPCONSISTING OF